... all kinds of formations of punching, drilling, casting, squeezing,etc.6. After using high-frequency local carburization heat treatment, ... standard of auto-lock screw.Four types of triangle self-tapping screws:1. After S TYPE general mechanical threaded, triangular ... , BUTTON, BRAZIER, FLAT, OVAL, PAN, ROUND, TRUSS, HEX etc.Common dirver type (DRIVER):PHILLIPS, POZIDRIV, SLOTTED, TRIANGLE, SQUARE, HEX ...